Amanda Knox is a no-show as new trial for murder begins in Italy

U.S. student Amanda Knox went on trial again for the murder of her roommate opened in Italy on Monday, but she was not in court.

Italy's highest court ordered a new trial for Knox and her former Italian boyfriend, overturning their acquittals in the 2007 slaying of Meredith Kercher with a harsh assessment of an appeals court acquittal in 2011. The Court of Cassation said the acquittal was full of "deficiencies, contradictions and illogical" conclusions.

The appellate court in Florence is expected to re-examine forensic evidence to determine whether Knox and her former boyfriend, Raffaele Sollecito, helped kill the 21-year-old Kercher while the two women shared an apartment in Perugia.

Sollecito was not present for Monday's proceedings, nor were Kercher's family members.

Knox, now a 26-year-old University of Washington student in Seattle, has not returned to Italy for the trial, nor is she compelled by law to do so. She is being tried in absentia with Knox's lawyers representing in court.

"We refute the idea that because Amanda is not coming, that Amanda is guilty, that Amanda is using a strategy. Amanda always said she was a friend of Meredith's, Amanda has always respected the Italian justice system," Knox's defense lawyer Luciano Ghirga told reporters before the trial opened.

Knox and Sollecito, now 29, have always denied having any role in the 2007 murder of Kercher, who was found with more than 40 wounds, including a deep gash in the throat.

Local bar owner Diya "Patrick" Lumumba, whom Knox falsely accused of being involved in the days following the murder, appeared in court Monday after being given the right to participate as a civil party damaged by the crime.

Lumumba's lawyers have insisted on participating in the retrial because Knox has not paid him the damages she was ordered to pay by court for unjustly implicating him.

In the stunning 2011 acquittal overturning lower court guilty verdicts against Knox and Sollecito and throwing out their long prison terms, a Perugia appeals court criticized virtually the entire case mounted by prosecutors. The appellate court noted that the murder weapon was never found, said that DNA tests were faulty and that prosecutors provided no murder motive.

Sollecito told NBC's TODAY on Monday that the proceedings were a "nightmare."

"It seems to be never-ending," he said. "It's a nightmare. My life is still on hold and I cannot move on, I cannot make plans for my future and I don't see a future for me. They destroyed my life in this period as well."

He added that he would attend the trial and give evidence if called to do so. "It is the decision of the court. I cannot make that decision by myself," he said.

Last week Knox told TODAY that it was "common sense" for her not to return to Italy for the retrial.

"I was imprisoned as an innocent person and I just can't re-live that," she said. "I thought about what it would be like to live my entire life in prison and to lose everything, to lose what I've been able to come back to and rebuild. I think about it all the time. It's so scary. Everything is at stake."

NBC News' Chapman Bell, The Associated Press and Reuters contributed to this report.